In previous studies on foreign body (FB) tumorigenesis in mice we have established the nature and the monoclonal orgin of tumor originator cells, have revealed FB-tumorigenesis as a multistage developmental process, and have described the changing etiologic role of the FB during the various sequential stages of the tumorigenic process. A method to culture, clone and expand in vitro the tumor originator cells during specific stages of preneoplastic maturation was developed. We are now in the process to derive in vitro clonal populations of tumor originator cells from the in vivo preneoplastic tissue at different defined stages of preneoplastic development beginning with the normal state up to full neoplastic autonomy. Such cell preparations will be used for comprehensive sequential analyses of cellular changes associated with the carcinogenic process. Specifically the following areas of study are anticipated: Histopathology, ultrastructure, chromosomes, cell growth kinetics (especially determination of proliferative thresholds), conditions for and degrees of in vivo tumorigenicity, cellular interactions, membrane phenomena; further (in cooperation with other laboratories) cellular biochemistry and regulation, cell genetics, membrane structure and function, and other specialized areas of cell research.